[Notabiker]

My wife and I bought a pre-owned 2007 frontier from the nissan dealer in town. We've constantly been getting 21mpg with it city driving. The lowest we've seen it drop was 18.5mpg. We got new tires for it that are a lot meatier and the MPGs dropped by 1mpg. Then we were averaging about 20mpg city. Not too shabby. We have since moved to Las Vegas and during the whole trip, which was entirely highway/interstate miles the gas mileage dropped and dropped and dropped and now that we've settled in we're getting 15.5 mpg. Highway and city. No matter how I drive, if I gun it from the start or if I ease on the gas pedal it's always the same.

I'm wondering if the higher altitude of Colorado was affecting the mileage in our favor. I've also heard that the ECU may need to be "reset" to learn the new driving conditions. Is this a possibility? I've been trying to avoid resetting it, but I've given it a good 1000 miles to try and relearn the habits, but nothing has changed.

We've tried all grades of gas and personally I try and stick to Shell or Chevron, but we've tried many different brands. There's no change at all.

I'll bring this one back from the dead just because I feel like it lol.

We moved to Co a few months ago and noticed the increase in mpg right away. Less air pressure means you get less power (3% for every 1k over sea level so here we get about 21% less power) like you have a smaller engine basically and the air is thinner so less resistance when driving means you get better mpg at the expense of acceleration. I've had my truck for almost a decade and never noticed the other valves kicking in at 3500 rpm until we moved here and I'm constantly revving higher just to get going.